Add support for reading the config path from env

This commit adds support to reading the config base path from the
environment variable `WAYBAR_CONFIG_DIR`. If it is set, but no
configuration is found there, it falls back to the previous mechanism
of using the default paths, without erroring.

include/config.hpp

@@ -14,6 +14,7 @@ namespace waybar {
 class Config {
  public:
   static const std::vector<std::string> CONFIG_DIRS;
+  static const char *CONFIG_PATH_ENV;
 
   /* Try to find any of provided names in the supported set of config directories */
   static std::optional<std::string> findConfigPath(

src/config.cpp

@@ -4,11 +4,14 @@
 #include <unistd.h>
 #include <wordexp.h>
 
+#include <filesystem>
 #include <fstream>
 #include <stdexcept>
 
 #include "util/json.hpp"
 
+namespace fs = std::filesystem;
+
 namespace waybar {
 
 const std::vector<std::string> Config::CONFIG_DIRS = {
@@ -16,12 +19,25 @@ const std::vector<std::string> Config::CONFIG_DIRS = {
     "/etc/xdg/waybar/",         SYSCONFDIR "/xdg/waybar/", "./resources/",
 };
 
-std::optional<std::string> tryExpandPath(const std::string &path) {
+const char *Config::CONFIG_PATH_ENV = "WAYBAR_CONFIG_DIR";
+
+std::optional<std::string> tryExpandPath(const std::string base, const std::string filename) {
+  fs::path path;
+
+  if (filename != "") {
+    path = fs::path(base) / fs::path(filename);
+  } else {
+    path = fs::path(base);
+  }
+
+  spdlog::debug("Try expanding: {}", path);
+
   wordexp_t p;
   if (wordexp(path.c_str(), &p, 0) == 0) {
     if (access(*p.we_wordv, F_OK) == 0) {
       std::string result = *p.we_wordv;
       wordfree(&p);
+      spdlog::debug("Found config file: {}", path);
       return result;
     }
     wordfree(&p);
@@ -31,10 +47,17 @@ std::optional<std::string> tryExpandPath(const std::string &path) {
 
 std::optional<std::string> Config::findConfigPath(const std::vector<std::string> &names,
                                                   const std::vector<std::string> &dirs) {
-  std::vector<std::string> paths;
+  if (const char *dir = std::getenv(Config::CONFIG_PATH_ENV)) {
+    for (const auto &name : names) {
+      if (auto res = tryExpandPath(dir, name); res) {
+        return res;
+      }
+    }
+  }
+
   for (const auto &dir : dirs) {
     for (const auto &name : names) {
-      if (auto res = tryExpandPath(dir + name); res) {
+      if (auto res = tryExpandPath(dir, name); res) {
         return res;
       }
     }
@@ -68,11 +91,11 @@ void Config::resolveConfigIncludes(Json::Value &config, int depth) {
   if (includes.isArray()) {
     for (const auto &include : includes) {
       spdlog::info("Including resource file: {}", include.asString());
-      setupConfig(config, tryExpandPath(include.asString()).value_or(""), ++depth);
+      setupConfig(config, tryExpandPath(include.asString(), "").value_or(""), ++depth);
     }
   } else if (includes.isString()) {
     spdlog::info("Including resource file: {}", includes.asString());
-    setupConfig(config, tryExpandPath(includes.asString()).value_or(""), ++depth);
+    setupConfig(config, tryExpandPath(includes.asString(), "").value_or(""), ++depth);
   }
 }